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GUIDANCE NOTES ON DISCHARGES FROM

VILLAGE HOUSES

Environmental Protection Department

28/F Southorn Centre

130 Hennessy Road

Wan Chai

Hong Kong


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CONTENTS

Page

Introduction 4

How does a Septic Tank System (STS) work 5

Control what goes into your STS 6

Inspect, desludge and repair your STS 8

What to do if your STS floods or overflows 11

Disposal of sullage 12

If your STS do not receive sullage 13

If you do not have a STS 13

Precautions when planning for a new STS 14

Connecting to communal sewer 15

Legal requirements under the Water Pollution Control Ordinance (WPCO) 17

Further information 17

Regional Office Boundary Map 19

Record of Inspection, Desludging and Repair Work 20

Some Immediate Action to take 24

List of contractors undertaking inspection, desludging and repair work 24

3


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Rainwater downpipe (not to STS)

Toilet waste system (to STS)

Sullage system (to STS)Toxic andexplosive

gases are produced in

the STS. Vent pipes are

installed to disperse

these gases into the

open air.

Surfacechannel

for rainwater

(not to STS)

Manhole coversshould not be

sealed with

cement.

Introduction

A Septic Tank System (STS) is the most common type of wastewater disposal system

for small village houses in areas where no communal sewer is available.

2. A STS can only perform well if it has been properly sited, designed, constructed,used, desludged and repaired when necessary.

3. A proper wastewater disposal system (including STS) should be installed for

the disposal of both toilet waste and sullage (i.e. wastewater from shower and

sink etc.). See diagram below. Disposal of sullage into surface channels can

be tolerated only if this does not result in pollution. Where necessary, the

Environmental Protection Department (EPD) may require the responsible

householder to install proper facilities (e.g. a STS) for the disposal of toilet

waste and sullage. Pollution associated with the incorrect disposal of

wastewater can result in prosecution under the Water Pollution Control

Ordinance.

WastewaterCollectionPipework

Toilet wastes and sullage (i.e.

wastewater from bath, shower,

sink, washing of clothes) are

collected by pipes to the STS.

Rainwater, which should be

discharged into stormwater

channels, should always be

excludedfrom theSTS.

SepticTank

Inside the septic tank, wastewater is partially

broken down and separates out into 3 layers, the

scum on the top, the sludge at the bottom, and

the main body of liquid which then becomes the

effluent from the septic tank. When the STS is

properly used, maintained and desludged, few

solids would leave the tank together with the

effluent.

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To prevent the ingress of

rainwater,manhole coverscan

be sealed with water repellent

grease, but not cement whichwould makeopening difficult.

The soil type and pit

configuration will

control the rate at

which the effluent

will soak away.

How does a Septic Tank System (STS) work?

4. A STS consists of a septic tank, a soakaway pit or some soakaway trenches,

and the surrounding soil into which wastewater is finally disposed. The septic

tank should be large enough to hold at least the volume of wastewater collected

in one day. The soakaway system and the surrounding soil should be able to

soak away the same volume in one day.

5. OVERFLOWfrom septic tank or soakaway pit, or direct discharge without

passing through a soakaway system, is POLLUTING and should not be

permitted.

6. Polluting material is only removed from the wastewater after travelling a long

distance in the soil. Pollution would result if a STS is located too near to a

beach, a stream, a well, etc., or even too near to a retaining wall where

wastewater might seep out from the face of the wall.

Soakawaypit

A soakaway pit has a perforated lining through which

effluent from the septic tank can soak into the

surrounding soil. This effluent contains dissolved

polluting material and also manysmall organisms

(pathogens) that can cause illness. Soakaway

trenches perform the same function as a soakaway pit,

but are usually more efficient.

SurroundingSoil

As the effluent seeps through the

surrounding soil, a process of

natural purification occurs. This

process includes the breakdown of

the polluting material by bacteria

occurring naturally in the soil, and

the eventual die off of the

pathogens. Adequate purification

can only be achieved after the

effluent has travelled a fairly long

distance through the ground.

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SaveWater

SaveMoney

PreventFlooding/Overflow

CONTROL WHAT GOES INTO YOUR STS

7. Don t overload your STS by discharging more than your STS can handle.

You should ensure that your STS has adequate capacity, especially before

letting your house as a holiday bungalow. If necessary, seek specialist

advice.

Overloading will lead to flooding or overflow

4 Ways to Prevent Overloading your STS and Save Water

Do not waste any water; use water sensibly

Do not flush your toilet unnecessarily

Take a brief shower instead of a bath

Use washing machine only when fully loaded

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Dispose of these wastes as refuse

8. Don t deposit any solid waste

other than human toilet waste

and a small amount of soft

toilet paper into your STS. Put

all other waste into a garbage

bin . Fit a screen at every

sink, wash basin and floor

drain. Screens fitted at all

drain openings and vent pipes

also help to control vermin.

9. Don t deposit excessive oil or chemicals into your STS. Oil will clog up pores in

the soil around the soakaway pit. Chemicals are generally toxic to the environment

and kill the bacteria (naturally occurring in the STS and the soil) which help to

remove the polluting matters in the wastewater.

7

Fix a screen

at all drains

andvent

pipes

Keep a waste bin

in your toilet

Not for solid wastes

other thanhuman

wastes and a small

amount of soft toilet

paper

Facial tissues, paper

towels, sanitary napkins,

condoms, etc.

Plastic or paper bags

and wrappingsWastecooking

grease& oil

Household waste chemicals

e.g. disinfectant, pesticide,

bleach, detergents,cleaning

agents, pharmaceuticals, etc.

Hair, needles, clips, pins,

toothpicks, cotton sticks,

straws, extinguished

cigarette ends, etc.

Screenings from sinks,

wash basins and floordrains, etc.

Food residues, wastes from

slaughteringof livestock


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Safety Measures

NEVER ENTERaSTS unless it has been

desludged & thoroughly

vented. Only experienced

personnel should enter a

STS.

Ste p 1

Use steel wires or nylon

strings to tie at least 80 cm

of white towelling firmly

onto a piece of bamboo or

wooden rod to make a

sludge measuring stick.

Please see diagram below.

Ste p 2

Make an opening in the

scum crust with a rod and

lower the sludge measuring

stick through the opening

to avoid the stick being

blackened by the scum

par tic les.

The soakaway pit and soil would be clogged veryeasily if solids were allowed to be carried into the

soakaway pit; this would happen if sludge were

allowed to build up to within 30 cm (1 ft.) of the

bottom of the outlet tee pipe or i f the outlet tee

pipe were broken.

Ste p 3

Thrust the measuring stick

through the sludge layer

forcefully to ensure that the

measuring stick reaches the

bot tom of the tan k.

Step 4

Measure the

depth of sludge.

SEPTIC TANK

White towelling will be

blackened by sludge

clinging to the towelling.

Scum

Inlet

chamber

Sludge

Outlet

chamber

OverallWaterDepth

80 cmSOAKAWAY PIT

Minimum

Bamboo or

Wooden Rod

White Towelling

Water Mark

INSPECT, DESLUDGE AND REPAIR YOUR STS

10. Do inspect your STS and measure the depth of sludge at least once every 6 months.

More frequent inspection and desludging might be necessary for heavily used STSs.

Inspecting Your STS

It is recommended that you hire experienced personnel to regularly inspect your

STS under your observation, and to desludge your STS whenever necessary.

11. Do inspect your STS immediately whenever

there is any flooding / overflow from your STS, foul smell becomes more noticeable, your toilet doesn t flush well or your sink doesn t drain well.

8

Blackened Length = Thickness of Sludge

SLUDGE MEASURING STICK Note : Desludging of the STS is necessary if this exceeds

30 cm (1 ft.) or 1/4 of overall water depth.

Overall Water Depth


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Inlet Tee-pipe

Outlet Tee-pipe

Vent pipe & screen

Drain openingsand screens

Drainage pipes

14. Do inspect if there is any defect in your drainage system or STS after each

desludging. If so, repair the defect before resuming discharge into your STS.

Any defects?

Check (Y/N)

15. Do keep a record of all inspection, desludging and repair work carried out at yourSTS. Use the table at the back of this book. A photograph can save a lot of words.

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16. Wheneveryou observeflooding/overflow from

your STS, you should:

Step 1 - Immediately reduce to an absolute

minimum the discharges from your

showers, baths, toilets and sinks etc.Step 2 - Inspect and desludge your STS.

Please consider emptying the whole

STS. The methods described in

paragraphs 10 and 12 should be

followed.

Step 3 - Let you r soakaway p it drain out

completely and then leave it empty

for at least 2 to 3 days fo r the

soakaway pit and the adjacent soil

to take a rest. If the soakaway pit

remains full, then you must empty it

by pumping. Resting can help

clogged soakaway pits to recover.

Step 4 - Continue to minimize water usage

after resuming discharge into the

STS. Only when satisfied that the

STS is working normally, should

y o u r e t u r n i t t o n o r m a l u s e .

Otherwise, see paragraph 18.

17. If you have had occasional flooding or overflow from your STS, especially after

rainfall, you should:

reduce water usage and minimize discharge as much as possible,

make no, or extremely little, discharge during rainfall and also on the day that

follows,

check that your water pipes are not leaking and that your water closets are notflushingcontinuously,

check that rainwater cannot enter your STS, and look into extending your STS, if suspected to be undersized.

What to do if your STS floods or overflows

11

Keep the

soakaway

pit empty

for at

least 2

to 3 days.

Resting

the

Soakaway


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18. If your STS continuously floods/overflows, and this has started within the

first year of using your STS, it is very likely that this is due to undersizing,

poor siting and/or poor construction of your STS. If minimizing water usage,

desludging and resting of the soakaway pit altogether had failed to prevent

flooding/overflow from your STS, you should seriously consider:

Investigating whether an extended, relocated or reconstructed STS would

improve the situation; specialist advice may be useful here. Please see

paragraph 24 as well.

Before improvement to your STS could be made, you should:

Use public latrines and public bath-houses as far as possible. Use all practicable means to maintain at an abso lute minimum the

discharges from your showers, baths, toilets and sinks, etc.

Inspect and desludge your STS frequently.

Enquiries on the Location of Public Bath-houses and Desludging Services

Food and Environmental Hygiene Department Hotline Tel. : 2868 0000

Disposal of sullage

19. For village houses built after 1984, the STS s should have been designed to

receive both sullage (i.e. wastewater from a bath, shower, sink or basin) and

toilet waste. However, for older village houses, most of the STSs had been

designed to receive only toilet waste. For some old village houses, no STS

had been provided at all. Sullage from these older village houses is commonly

discharged via surface channels to the nearby streams. Disposal of sullage

into surface channels can only be tolerated if this does not result in pollution.Where necessary, the EPD may require the responsible householder to install

proper facilities (e.g. a new STS) or extend the existing STS for the disposal

of both toilet waste and sullage.

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22. Sullage discharged into surface channels shall notcontain any waste or polluting

matter such as faeces, blood and waste from slaughtering livestock, sludge or

solid refuse of any kind, food residues or other waste that are liable to form

scum or deposit. Only relatively clear wastewater reasonably free of

chemicals, visible solids, oil and foam, and discharged via fine screens, may

be permitted to be disposed of into surface channels.

If you do not have a STS23. If you do not have a STS and you are not served by a communal sewer, you

should:

NOT install or use a flushing toilet in your house,(see paragraph 24 if you want to use a flushing toilet)

use public latrines and public bath-houses as far as possible,

dispose of night soil properly, e.g. to public latrines, put food residues, etc., into your garbage bin, dispose of sullage via fine screens, and remove the screenings into

your garbage bin, and

pay special attention to paragraphs 21 and 22 above.If you have or are planning for a flushing toilet in your house, you should

install a proper wastewater disposal system (e.g. a STS).

If your STS do not receive sullage20. If your STS do not receive sullage, you

should adopt all practicable means to

reduce the amount of pollutants in the

sullage that you discharge into surface

channels.

You should: d i s c h a r g e o n l y w a s t e w a t er containing very little pollutants via

fine screens into surface channels,

d i spose of d i r ty d i shwashingwastewater via toilet bowl into

your STS, and

minimize your water usage toe n s u r e t h a t y o u r S T S i s n o t

overloaded.

21. You should properly maintain your surface

channels and ensure that your wastewater

discharge will not pond in surface

channels or fields nearby and become a

source of pollution.

13

Reuse bath wateror laundry waterfor toilet flushing

Pour dirty dishwashingwashwater into toilet bowl,

preferablyat times whenflushing of toilet is necessary

Flush as few timesas possible

Finescreen

Surfacechannel

FineScreens (A greenplastic fine net availablefrom hardware storescan be folded intodouble layers and usedas a finescreen)


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Precautions when planning for a new STS

24. Remember PREVENTION IS BETTER THAN CURE.

Before you decide to construct a new STS

either to serve your new village house,

or to replace your problematic STS,or to extend your undersized STS,

or to match your plan to install flushing toilets and shower etc. in

your house, you should:

(a) ensure first that there is no communal sewer available into which

you could connect (see paragraph 35). Approach nearby

developments to consider the possibility of a joint connection to

communal sewer being made;(b) examine the feasibility of a STS, and carry out a soil percolation

test before deciding to construct a STS;

(Note : A STS is not feasible in areas

i) prone to flooding during storms,

ii) with high groundwater table, OR

iii) with impermeable soil.)

(c) locate and size your STS suitably, and allow adequate land for

its construction , i.e.

i) do not locate your STS near streams, wells, retaining

walls, etc., or beneath your house,

ii) size your STS according to your anticipated maximum

discharge loading and the absorption capacity of the local

soil (based on soil percolation test results obtained

beforehand), and

iii) locate your STS in an open space with easy access for

desludging;

(d) investigate the possibility of constructing a communal STSor communal sewage treatment plant; (This will probably help

to alleviate problems associated with scarcity of land for

individual STS s, poor soil permeability and sites too close to

streams etc.); and

(e) SEEK SPECIALIST ADVICE WHENEVER YOU ARE IN

DOUBT.14


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Connecting to communal sewer

25. The most effective and reliable way to dispose of wastewater is by connecting

to communal sewers leading to government treatment facilities.

By connecting to communal sewers, you will:

enjoy a safer and healthier living environment; stop pollution caused by malfunctioning STS; not need to operate, maintain and monitor STS; and comply with pollution control legislation easily.

26. The Government has plans to provide new sewers and improve existing

communal sewers in the territory. Most premises not currently served by

communal sewers will gradually be provided by one.

27. When communal sewers are provided

i n t h e v i c i n i t y a n d r e a d y fo r

connection, EPD may send you a

notice requiring you to construct

appropriate terminal manhole and

other pipework for conveying all your

wastewater to the communal sewer

before a specified date.

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16

28. The responsible householder is to construct and pay for the terminal manhole

and any pipework leading from the village house to the terminal manhole.

The Government will provide and pay for the new communal sewers and

the sewer linking the terminal manhole to the communal sewer.

29. You should properly maintain the

terminalmanhole constructed and any

pipework leading from your village

house to the terminal manhole.


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17

Legal requirements under the Water Pollution Control Ordinance (WPCO)

30. The introduction of the Water Pollution Control Ordinance has allowed the

government to ensure that everyone becomes responsible for his/her part in

protecting the environment of Hong Kong. This Ordinance operates through alicensing system to control the discharge of sullage and the use of STSs.

31. If you possess a STS, or discharge sullage, it is advisable for you to obtain a

licence from the EPD, and comply with the licence conditions in order to avoid

any conviction for polluting the environment. However, a licence will not be

required if your house is connected to communal sewers.

32. EPD will inspect STSs and associated drainage systems to ensure that they areproperly used, desludged and maintained. EPD might issue a warning letter to

the responsible householder requiring improvements to the STS and associated

drainage systems, including where necessary the installation of a new wastewater

disposal system. Should the responsible householder fail to provide the necessary

improvements as required, EPD may take prosecution action.

33. When communal sewers are available in the vicinity, EPD may issue a notice

requiring the responsible householder to connect all wastewater generated fromthe village house to the communal sewer. It will be an offence if the householder

does not comply with the requirement in the notice.

Further information

34. For further enquiries and collection of WPCO licence application form, you can

contact Regional Offices of EPD:

Regional Office (East) Regional Office (South)

5/F Nan Fung Commercial Centre, 2/F Chinachem Exchange Square,19 Lam Lok Street, 1 Hoi Wan Street, Quarry Bay, Hong Kong.

Kowloon Bay, Kowloon. Tel. : 2516 1718

Tel. : 2755 5518 Fax : 2960 1760

Fax : 2756 8588

Regional Office (West ) Regional Office (North)

8/F Tsuen Wan Government Offices, 10/F Shatin Government Offices,38 Sai Lau Kok Road, No.1 Sheung Wo Che Road,

Tsuen Wan, New Territories. Shatin, New Territories.Tel. : 2417 6116 Tel. : 2158 5757

Fax : 2411 3073 Fax : 2685 1133


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The map on Page 19 shows delineation of respective Regional Offices.

Application forms can be also be obtained from the following District Offices:

Southern District Office, Stanley Sub-office, Islands District Office, Mui Wo Sub-

office, CheungChau Sub-office, North District Office, Sai Kung District Office,Tsueng

Kwan O Sub-office, Sha Tin District Office, Tai Po District Office, Tuen Mun District

Office and Yuen Long District Office.

35. For information on existing communal sewers, you can contact the following

divisions of the Drainage Services Department :

Address Telephone Fax

Hong Kong and Islands 42/F, Revenue Tower, 2594 7175 2827 6657Division 5 Gloucester Road,Hong Kong

Mainland South Division 15/F, Kowloon Government Offices, 2300 1441 2771 9640405 Nathan Road,Kowloon

Mainland North Division 14/F, Kowloon Government Offices, 2300 1441 2770 4761405 Nathan Road,Kowloon

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19


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20

RECORD OF INSPECTION DESLUDGING

AND REPAIR WORK

INSPECTING

Date of Inspected by Sludge thickness Remarks on any flooding/ Date ofinspection whom (see P.8) overflow/clogging observed desludging

(see P. 11 & 12)

e.g.

03/01/92 Chan Tai-man 30 c.m. No problem 20/01/92(or 1 ft.)


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21

DESLUDGING REPAIRING

Desludged Desludging Sludge Defects observed Date of Repairedby whom method disposal (see P. 10) repairing by whom

(see P. 9) (see P. 9)

ABC Pump Lorry No. AB Outlet tee-pipe in 22/01/92 ManDesludging 1234 to Sai septic tank is Kee Co.Co. Kung STW rotten


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22

RECORD OF INSPECTION DESLUDGING

AND REPAIR WORK

INSPECTING

Date of Inspected by Sludge thickness Remarks on any flooding/ Date ofinspection whom (see P.8) overflow/clogging observed desludging

(see P. 11 & 12)


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23

DESLUDGING REPAIRING

Desludged Desludging Sludge Defects observed Date of Repairedby whom method disposal (see P. 10) repairing by whom

(see P. 9) (see P. 9)


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Some Immediate Action to take

1. Is your house connected to a communal sewer?

If not, please keep this book in your house and follow its recommendations.

2. Do you have a STS?

If not, please read paragraphs 19 and 23 carefully again now!

3. Does your STS receive sullage?

If not, please read paragraphs 19, 20, 21 and 22 carefully again now!

4. Have you inspected your STS in the last 6 months?

If not, please read paragraph 10 again and inspect now!

5. Have you applied for a WPCO licence?If not, please read paragraphs 30, 31 and 32 carefully again now!

6. Does your STS flood / overflow occasionally?

If so, please read paragraph 17 carefully again now!

7. Does your STS flood / overflow continuously?

If so, please read paragraph 18 carefully again now!

8. Are you planning for a new STS?

If so, please read paragraphs 24 and 35 carefully again now!

PLEASE DONT DELAY ATTENTION TO YOUR STS PROBLEMS!

List of contractors undertaking inspection, desludging and repair work

Name Tel. No. Services provided

RememberINSPECT YOUR STS ONCE EVERY 6 MONTHS

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